1. Field of the Invention
The present invention pertains to a method for manufacturing a silicon carbide (SiC) semiconductor device (hereinafter referred as xe2x80x9cthe SiC devicexe2x80x9d) in which a silicon oxide (SiO2) film is formed on a SiC substrate and an oxidation furnace suitable for the method.
2. Description of the Related Art
It is known that SiC crystal has thermally and chemically stable crystallographic and electric performances. And the SiC crystal has electric break down characteristic better than that of Si. Among SiC crystals, 4Hxe2x80x94SiC, whose band gap is, specifically, approximately three times larger than that of silicon (Si) is a strong candidate for a power device, because it can manifest a very high breakdown characteristics. And the applications of the power SiC device, which can operate with a higher voltage and higher power, to power electronics fields, such as the control system and the like are expected. In the SiC substrate, the bond energy between Si and C in the SiC single crystal has about 1.34 times larger compared to the bond energy between Si and Si in the Si single crystal.
Manufacturing the SiC device embracing these superior device behaviors by forming a thermal oxide film on the surface of the SiC substrate has been attempted, but the fabrication technology of the SiC device encompassing desired performances in a short manufacturing period has not yet been established.
An object of the present invention is to provide a method for manufacturing the SiC device having a desired performance by forming a silicon oxide film on the surface of the SiC substrate in a short manufacturing period.
Another object of the present invention is to provide a method for manufacturing the SiC device having an improved gate oxide film embracing smaller interface state densities.
Still another object of the present invention is to provide an oxidation furnace suitable for a method for manufacturing the SiC device, especially forming a silicon oxide film on the surface of the SiC substrate in a short manufacturing period.
First feature of present invention inheres in a method for manufacturing a SiC device, embracing (a) depositing a silicon film above a SiC substrate; (b) delineating the silicon film into required pattern; and (c) annealing the SiC substrate in a water rich ambient to selectively grow a localized thermal oxide film above the SiC substrate.
Second feature of present invention inheres in a method for manufacturing a SiC device, encompassing (a) forming a gate oxide film on a surface of a SiC substrate; and (b) annealing the gate oxide film in a water rich ambient at substrate temperature equal to or lower than the substrate temperature at which the gate oxide film is formed.
Third feature of present invention lies in an oxidation furnace encompassing (a) a reaction tube; (b) a boat configured to mount a SiC substrate; (c) a heater configured to heat the SiC substrate; (d) oxygen gas introduction tube connected to an upstream side of the reaction tube; (e) a mass flow controller connected to the oxygen gas introduction tube configured to control a flow rate of oxygen gas; (f) a water introduction tube connected to the upstream side of the reaction tube; and (g) a conveying pump configured to introduce an ultra pure water into the reaction tube through the water introduction tube.
Fourth feature of present invention lies in an oxidation furnace encompassing (a) a reaction space defining means for causing thermal oxidation phenomena therein; (b) a mounting means for mounting a SiC substrate; (c) a heating means for heating the SiC substrate; (d) oxygen gas introduction means for introducing an oxygen gas into the reaction space defining means; and (e) a water introduction means for introducing an ultra pure water into the reaction space defining means such that H2O partial pressure in the reaction space defining means is controlled to any values between 0 to 1.
Other and further objects and features of the present invention will become obvious upon an understanding of the illustrative embodiments about to be described in connection with the accompanying drawings or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employing of the present invention in practice.